body {
  font-family: Arial, sans-serif;
  margin: 20px;
}
h2 {
  color: #333;
}
.form {
  margin-bottom: 10px;
}
button {
  margin: 5px;
  padding: 5px 10px;
}
canvas {
  display: block;
  margin-top: 15px;
  border: 1px solid #ccc;
}
pre {
  background: #f9f9f9;
  padding: 10px;
  border: 1px solid #ddd;
  max-height: 200px;
  overflow: auto;
}